(1) Field of the Invention
The present invention relates to a structure of felt for papermaking, specifically to an optimum structure of the felt used in a high speed tissue paper machine for assuring smoothness of the paper, prompt papermaking stability after beginning the operation of the machine, compatibility, and durability.
(2) Description of Related Art
For a paper machine, the structure of felt for papermaking used for dewatering of wet paper is ordinarily composed of a substrate made of seamless woven fabric, and a batt layer prepared by implanting batt fibers of short fibers onto the substrate by the needle-punch technique. There are provided structures of pluralities of batt layers for the above felt, (Patent Documents 1, 2, 3, and 4).
The above felt with a multilayer structure adopts thin fibers with small fineness as the uppermost layer of the felt, contacting with the wet paper. The reason for using small fineness fibers is to improve the smoothness of the uppermost layer which contacts the wet paper, so that the surface smoothness of the wet paper can be improved.
Since an intermediate layer between the uppermost layer of the felt and the substrate thereof does not contact the wet paper, relatively coarse fineness and rather thick fibers are used in the intermediate layer to keep the water permeability of the felt for a long period of time. With that structure, crush of the intermediate layer is suppressed during a specified use period of time, and the surface smoothness of the wet paper is improved to some degree.
[Patent Document 1] JP-A-50-43204, (the term “JP-A” referred to herein signifies the “Unexamined Japanese Patent Publication”);
[Patent Document 2] JP-A-6-123094;
[Patent Document 3] JP-A-7-150496;
[Patent Document 4] BP Publication No. 2,200,867;
[Patent Document 5] JP-A-8-506863;
[Patent Document 6] JP-A-5-214694; and
[Patent Document 7] U.S. Pat. No. 6,175,996